The instant invention resides in the art of stereo sound apparatus, and more particularly in that of stereo generators and dynamic range expanders.
In recent years, there has been a great increase in the popularity of stereo sound systems for retrieving the tonal image stored upon the modulation sidewalls of a record groove. With the increase in popularity has come a number of attempts to sophisticate and refine such stereo systems to improve channel separation, noise suppression, frequency response, and the like. Indeed, in U.S. Pat. No. 3,040,136, to J. F. Grado, a number of advances were made in the art. In applicant's own copending patent application Ser. No. 949,742, for "STEREO CARTRIDGE," filed Oct. 10, 1978, still further improvements in the art have been set forth. The structure of the instant invention yet further advances the art beyond the point to which it has been taken by the teachings of Grado and those of applicant's referenced application.
In the prior art, other stereo systems have customarily emitted a low level sound known as "record hiss," particularly when the volume of the stereo amplifier has been increased to enhance loud sounds. Record hiss is a low level sound, but with the increase in amplifier volume, the hiss is accentuated and becomes audible to the discerning listener. Yet further, low level harmonics of the tonal image recovered by the stereo system from the record have often been lost in present systems utilizing an armature for saturating electromagnetic coils with magnetic flux. Such armatures have had a tendency to magnetize with time and to thus maintain a residual magnetization in the range actuated by low level harmonics. With an existing threshold of residual magnetization upon the armature, the coils have been incapable of responding to or recognizing low level harmonics from the tonal image.
In the prior art, other problems have existed with the general mechanical structure of the stereo pick-up cartridge and generator. Indeed, there are no known systems, apart from applicant's own, which utilize a shank assembly and associated moving generating elements which may be readily removed from a cartridge assembly and be easily replaced without the need for special tooling and the like. Heretofore, such removal has generally resulted in the costly discarding of the stereo pick-up itself and the subsequent total replacement of the same.
Additionally, known systems have generally been ineffective in optimizing full frequency bandwidth channel separation, but have allowed cross-talk between channels without reliably correlating the mechanical modulation of the sidewall of a record groove with the associated output channel of the stereo system.
Additionally, known systems have required sophisticated and expensive add-on equipment to achieve dynamic range expansion or enhancement. All known dynamic range expanders have been totally electronic in nature and there are no known electromechanical assemblies and particularly no such assemblies which may be found directly within a cartridge or pick-up other than that taught by applicant's copending patent application.
The vast majority of stereo cartridge generators known to applicant utilize elastomers as fulcrums for the moving iron or moving magnet signal inducers of the stereo pick-up. Such elastomers inherently result in audible distortion since such elastomers subject the fulcrum to random mispositioning. Hence, response of the signal inducer attached thereto is not a true electrical reproduction of the tonal modulations stored within the stereo record grooves.